Approx. 6 million tonnes of old electrical appliances accumulate in Europe every year. Approximately a fifth of this waste is plastic materials. The EU guideline 2002/96/EC (WEEE directive) demands high salvage quotas which can only be achieved with a material recycling method for the plastic material fractions.
However, material recycling for plastic materials from old electrical appliances is not state of the art because of the material diversity thereof and because of the high pollutant content thereof. There should be mentioned as pollutants the obsolete brominated flame-retardant additives with a high potential for dioxin formation. New works also verify toxic effects of brominated flame retardants themselves, in particular PBDE and PBB.
These additives which were often used previously and which are disposed of with the current old electrical appliances are thus subject in the meantime to prohibitions and strict limits: 2002/95/EC RoHS guideline and Penta guideline 2003/11/EC.
Material recycling of plastic materials from electronic scrap firstly requires material sorting since, in electronic scrap, at least 15 different types of plastic material which are as a rule incompatible must be anticipated. Material sorting can be effected via spectroscopic methods on large plastic material parts (housings of visual display units) or for material sorting of plastic material-containing shredder fractions via a density separation. The latter makes it possible to separate, in a two-stage process, acrylonitrile-butadiene-styrene (ABS) and polystyrene (PS) of a light polyethylene/polypropylene fraction and also of a heavy PVC-rich fraction. Separation of flame-retardant materials based on bromine and non-flame-retardant materials of the middle fraction (ABS and PS) is not effected.
The company Hamos offers the surface discharge spectrometer Slide-Spec-S2 with which simultaneous detection of the type of plastic material and also identification of bromine-containing flame retardants can be effected (http://hamos.com/en/products/plastic-identification.htm).
For disposal of plastic material waste equipped in part with brominated flame-retardant additives from plastic material shredder separation, thermal and raw material methods have therefore been developed, e.g. pyrolysis, such as Haloclean inter alia or Schwarze Pumpe (Uddin, M. A.; Bhaskar, T.; Kaneko J.; Muto, A.; Sakata, Y.; Matsui, T. (2002) “Dehydrohalogenation during pyrolysis of brominate flame retardant containing high impact polystyrene (HIPS.Br) mixed with polyvinyl-chloride (PVC), Fuel 81, pp. 1819-1825).
For high-grade material recycling of the contained plastic materials, various chemical and physical methods have been developed for separation of brominated flame-retardant additives in the laboratory and on a small industrial scale. There are included herein reductive halogenation, as described in Mäurer, A., Schlummer, M. (2004) “Good as new. Recycling plastics from WEEE and packaging waste.” Waste Management World, May-June 2004, pp. 33-43, or also selective extraction (Von Quast, O. (1996): Universal method for dehalogenation of thermoplasts. Dissertation at Berlin TU, series of papers on plastic material research 36, editor Prof. Käufer, and EP 0 949 293).
The above-mentioned surface discharge spectrometer can only be used for large plastic material parts and not for automated sorting of shredder plastic materials, i.e. is not suitable for large scale industrial application. Application in specialised dismantling operations is possible but only with high specific time expenditure.
It is disadvantageous in the mentioned thermal and raw material methods that new petrochemical raw materials are produced at best or only the calorific value of the plastic materials is used.
Chemical methods (reductive dehalogenation) require use of expensive reduction agents (e.g. pure sodium) which require in addition a water-free operation, i.e. a very thorough, energy-intensive drying of the waste.
In contrast, the above-mentioned physical methods, which operate on the principle of different solubility characteristics of polymer and flame-retardant additive, display weaknesses in the separation of additives which are difficult to dissolve, in particular decabromodiphenyl ether (DBDE) and 1,2-bis-tribromophenoxy ethane (TBPE). In addition, larger quantities of solvent are required which generally must be recovered by distillation.
Furthermore, the disadvantage of the mentioned thermal, raw material, chemical and physical methods is that the conversion involves high investment costs and can only be operated economically with high throughput quantities (>1000 tonnes per year).
It was therefore the object of the present invention to eliminate the described disadvantages of the state of the art and to provide a method which is easy to operate and therefore economical and which allows separation of flame-retardant-free industrial plastic materials.